The synthesis of 2-Bromo-9-fluorenone is as follows:the 9-fluorenone (10mmol), the phase transfer catalyst (1.5mmol fourteen alkyl trimethyl ammonium chloride) and brominated aqueous ammonium solution (30 wt %, 25mmol ammonium bromide) mixing and heating system temperature to 75 °C, in 1h is divided into three time 11mmol potassium bromate, to three times the weight ratio of 1:3:1, to maintain the system temperature to continue reaction 3h, wherein the 9-fluorenone, ammonium bromide, the molar ratio of potassium bromate 1 : 2.5: 1.1 ; 9-fluorenone, and fourteen alkyl trimethyl ammonium chloride (phase-transfer catalyst) molar ratio of 1 : 0.15; 2) after the reaction, to room temperature, by adding 20% aqueous solution of sodium sulfite ( eliminates the bromine fluid ), is filtered, the filter cake washing water And dried to obtain yellow solid of 2-Bromo-9-fluorenone, the yield is 99.2%.